The importance of pneumocandin B0 as the fermentation-derived starting material for the antifungal drug candidate, MK-991, along with the identification of our production strain as Z. arboricola (ATCC 20868) as CBS prompted a search for other strains of Z. arboricola or Zalerion species with improved titres or that might produce natural pneumocandin analogues. Analysis of morphology, secondary metabolites profiles, and DNA fingerprinting demonstrated that ATCC 20868 was not congeneric with Z. arboricola. Ribosomal DNA sequences were compared among Zalerion species and pneumocandin-producing fungi and with rDNA sequences in GenBank. No good matches with sequences in GenBank were obtained for Z. arboricola or Z. maritimum, but for Z. varium, P. carpinea and ATCC 20868, relevant similarities were observed with ITS1 sequences from fungi of Leotiales. ATCC 20868 was phylogenetically more akin to P. carpinea, another pneumocandin producer, than initially suspected. The closest relative of ATCC 20868 seemed to be Hymenoscyphus monotropae. We conclude that the genus Zalerion is artificial; its species bear no phylogenetic relation among themselves. ATCC 20868 and Z. varium were related to fungi of the Leotiales. We propose a new anamorph genus and species, Glarea lozoyensis, to accommodate ATCC 20868.